Field of the Invention
The present disclosure relates to a sheet detection mechanism to be mounted on an image forming apparatus, such as a printer and a copying machine using an electrophotographic technique and an image forming apparatus equipped therewith.
Description of the Related Art
Image forming apparatuses using an electrophotographic technique are equipped with sheet detection mechanisms for detecting moving sheets and fixing units for heat fixing images on sheets. However, if the sheet detection mechanism exists near the fixing unit, there is a possibility that water vapor generated from a sheet by heat fixing causes dew condensation in the sheet detection mechanism, and the sheet detection mechanism is thermally damaged by radiation heat from the fixing unit.
Japanese Patent Application Laid-Open No. 2007-33520 describes a configuration for cooling a sensor for detecting a sheet by blowing air thereto.
As a type of a sheet detection mechanism for detecting a sheet by illuminating a sheet with light, there is a configuration in which a part of a sensor unit is disposed on both of two guide units disposed to face each other across a sheet conveyance path. For example, a light-emitting unit is arranged on one of the guide units, and a light-receiving unit for receiving light and converting it into an electrical signal is arranged on the other guide unit. When a conveyed sheet blocks the light, presence of the sheet is detected. However, when the sensor unit is cooled by being blown by air in the configuration in which the part of the sensor unit is disposed on both of the two guide units, at least two air ducts are required, and the apparatus becomes larger.